I tried the voltmod today on my 1.15y. Works like a charm. Went from 216 to 232 after raising the voltage to 1.32V. Also tried 1.4V for a short time, which gave me

001-0: ztex_ufm1_15y1-04A36E42D1-4: f=248.00MHz,  errorRate=0.00%,  maxErrorRate=0.00%,  hashRate=248.0MH/s,  submitted 13 new nonces,  luckFactor=0.66

Now I am thinking about watercooling, also because of the noise reduction and about recompiling BTCMiner to allow higher frequencies ;-)